Reliability of human cryopreserved hepatocytes and liver microsomes asin vitrosystems to predict metabolic clearance

Abstract

A total of 110 drugs, selected to cover a range of physicochemical and pharmacokinetic properties, were used to explore standard approaches to the prediction of in vivo metabolic clearance using drugdepletion profiles from human liver microsomes (HLMs) and cyropreserved hepatocytes. A total of 41 drugs (37% of the compounds tested) showed measurable depletion rates using HLMs (depletion by 20% or more over the time course). The most reliable correlations in terms of bias (average fold error (AFE) ¼ 2.32) and precision (root mean square error (RMSE) ¼ 3501) were observed by comparing in vivo intrinsic clearance (CL int ), calculated using the parallel-tube model and incorporating the fraction unbound in blood, with in vitro CL int adjusted for microsomal binding. For these reference drugs, 29% of predictions were within two-fold of the observed values and 66% were within five-fold. Compared with HLMs, clearance predictions with cryopreserved hepatocytes (57 drugs) were of similar precision (RMSE ¼ 3608) but showed more bias (AFE ¼ 5.21) with 18% of predictions within two-fold of the observed values and 46% within five-fold. However, with a broad complement of drug-metabolizing enzymes, hepatocytes catalysed measurable CL int values for a greater proportion (52%) of the reference compounds and were particularly proficient at defining metabolic rates for drugs with predominantly phase 2 metabolic routes.

Meeting the Challenge of Predicting Hepatic Clearance of Compounds Slowly Metabolized by Cytochrome P450 Using a Novel Hepatocyte Model, HepatoPac

“…Clearly, possible differences in specific P450 content between donors could also contribute to these differences. In comparison, Stringer et al (2008) noted that perceptible turnover could only be observed with 3 of 24 reference drugs (13%) with low to intermediate in vivo CLint (ranging from 1 to 10 mL/min/kg).…”

“…One of the key challenges in using suspended hepatocytes for predicting hepatic clearance is the loss of activity of drug metabolizing enzymes that restricts the typical incubation period to 4-6 hours (Elaut et al, 2006;Stringer et al, 2008). This limited incubation time prohibits the accurate determination of the intrinsic clearance (CL int ) of compounds that are slowly metabolized.…”

Metabolite Formation Kinetics and Intrinsic Clearance of Phenacetin, Tolbutamide, Alprazolam, and Midazolam in Adenoviral Cytochrome P450-Transfected HepG2 Cells and Comparison with Hepatocytes and In Vivo

“…The CL int and CL max values were compared with the equivalent values obtained using the commonly used suspended human cryopreserved hepatocyte system for phenacetin (Stringer et al, 2008), tolbutamide (Brown et al, 2007), alprazolam (Brown et al, 2007), and midazolam (Brown et al, 2007) after multiplication by the appropriate RAF (above). The CL int and CL max values scaled to in vivo were compared with the equivalent human in vivo CL int values for phenacetin (Stringer et al, 2008), tolbutamide (Brown et al, 2007), alprazolam (Brown et al, 2007), and midazolam (Brown et al, 2007).…”

Predicting when Biliary Excretion of Parent Drug is a Major Route of Elimination in Humans

“…While human liver microsomes generally provide reliable predictions of human metabolic clearance for extensively metabolized drugs (8)(9)(10)(11)(12)(13) and renal clearance is not difficult to determine, predictions of human biliary clearance are difficult and scarce, despite ongoing efforts (14). Clinical methods include bile duct cannulation during surgery, collection of duodenal fluid in healthy volunteers, or fecal collections.…”